Abstract
The structural differences of lateral roots in rice plants were investigated in relation to their diameters. 1. Among the lateral roots of any type investigated, whether they were "thick"laterals with further branching ability or "thin" ones with no such ability, the thinner ones tended to diminish their structural complexities quantitatively, i. e. the thickness of cortex, the number of cortical layers, the diameter of the stele, and the number as well as the diameter of vessels decreased, respectively, in proportion to the root diameters. 2. The same relation was found when the structures were examined along an axis of each "thick" lateral root with diameter acropetally decreasing. 3. The apical axial parts of such "thick" lateral roots were found to be closely alike to the "thin" ones both in diameter and in structure, and in these parts no further branching was recognized. Based on these results, it was suggested that there exist a close interrelation among the diameter, the structure and the branching ability of lateral roots, regardless of their types, being " thick" or " thin".
